We study the trade-off between energy harvesting and data communication for a two-meter wireless galliumarsenide vertical-cavity surface-emitting laser and photovoltaic link. The use of orthogonal frequency-division multiplexing with adaptive bit and power loading results in a peak data rate of 1041 Mb/s at a bit-error ratio (BER) of 2.2 × 10 −3 under short-circuit conditions. The receiver is shown to provide power harvesting with an efficiency of 41.7% under the irradiance of 0.3 W/cm 2 and simultaneous data communication with a rate of 784 Mb/s at a BER of 2.8 × 10 −3. The experimental system is envisioned to become a paradigm for next-generation wireless backhaul communications and Internet-of-Things applications.

The application of wireless backhaul communication and power transfer to outdoor small cells (SCs) could significantly decrease their installation cost. In this paper, the concept of indoor optical wireless power transfer (OWPT) to SCs is investigated in the absence of ambient light, i.e. during darkness hours. An experimental study is conducted by the use of up to 4 red laser diodes (LDs), a crystalline silicon (c-Si) solar panel and cell placed at 5.2 m. A value of 69% is measured for the fill factor (FF) of the solar panel. Also, a total power efficiency of 3.2% is measured for an optical wireless (OW) link with an average efficiency of 2 LDs of 26.8%, a solar cell efficiency of 13.3% and only 10.6% of geometrical losses. A comparison of this link with a state-of-the-art inductive power transfer system (IPTS) shows an improvement of the total link efficiency by 2.7 times. Another OW link is implemented with a divergence of full width at 36.8% of the peak intensity of 3 mrad and 5.75 mrad along the small and large axes of the beam, respectively. The experimental levels of harvested power are in the order of mW, whereas approximately 1 W is required for the operation of a SC. Therefore, a 42 laserbased transmitter is designed both analytically and by the use of the simulation tool Zemax. The respective results show the feasibility of delivering 7.2 W of optical power to a solar cell of up to 30 m distance with geometrical losses of only 2%, but a beam enclosure is also required due to eye safety restrictions.Index Terms-Small cells (SCs), optical wireless power transfer (OWPT), energy harvesting (EH), radio frequency (RF), rectennas, diode lasers, quantum well lasers, laser beams, solar energy, energy efficiency.

In this letter, we demonstrate for the first time the additional capability of high-speed data communication for single-junction photovoltaic (PV) cells. A record 3-dB bandwidth of 24.5 MHz is reported for a gallium arsenide (GaAs) PV cell. The PV cell is shown to achieve a power efficiency of at least 42% when irradiance of 0.46 W/cm 2 is received from 847-nm verticalcavity surface-emitted laser. Optimized bit-and-power-loaded optical orthogonal frequency-division multiplexing (OFDM) is applied to use the communication bandwidth most efficiently. With this, a data rate of 0.5 Gb/s is achieved for a 2-m OFDMbased laser link. To the best of our knowledge, the reported data rates achieved with a GaAs PV cell as the detector are the highest for simultaneous optical wireless information and power transfer.

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